±6S 



Dr. W. F. (i. Swarm on the Electrical 



# -2 , on cooling the film down to liquid-air temperature 

 (-180° C.) we should have \_i 80 Ao = (273/93) 2 = 8'58, so that 

 the distance of the bend from the origin of thickness should 

 be, at liquid-air temperature, 8*58 times its value at 0° 0. 



It was found that no such displacement of the bend took 

 place, and apart from certain relatively small variations of 

 the resistance of the films with temperature, which will be 

 discussed later, the curves at the two temperatures were 

 practically coincident, at any rate in the neighbourhood of 

 the bend. The experiments are not taken as necessarily 

 proving that \ does not vary as #~ 2 , but rather as showing 

 that the explanation of the sharp bend is to be found from 

 another standpoint than that which explains it as due to the 

 thickness of the film becoming comparable with the mean 

 free path. It will be more convenient to discuss this point 

 after the apparatus and experiments have been described. 



Fig-. 1. 



M 



^-- r JUUUUUULL- | 



Apparatus and Experiments. — The films were deposited by 

 sputtering from a platinum cathode in vacuo, and all the 

 films corresponding to a single set were deposited in the 

 same vacuum. In this way a greater uniformity of the rate 

 of deposition can be obtained than in the case where the 

 apparatus is taken down after the deposition of each film, 

 as in the experiments of Patterson. The apparatus is 

 represented in fig. 1. 



The cathode C, which consisted of a piece of platinum foil 



